1. Field
The present disclosure relates generally to inspecting materials and in particular to a method and apparatus for inspecting transparent materials. Still more particularly, the present disclosure relates to a method and apparatus for inspecting a transparent material attached to a frame or other component.
2. Background
An aircraft canopy is a transparent enclosure for the cockpit that may be used on some types of aircraft. The function of a canopy is to provide a weather proof and reasonably quiet environment for the occupant or occupants of the aircraft. A canopy is typically aerodynamically shaped to minimize drag on an aircraft. A canopy includes a transparent material that is captured or attached to a frame. This transparent material may be, for example, glass or acrylic. The transparent material is also referred to as a transparency. The frame of the canopy is attached to the aircraft and allows the canopy to move, or open and close. The transparency typically is machined to include a row of holes around the periphery to attach the transparent material to a structural frame. This transparency is then attached to the frame with fasteners, such as bolts or other fastening system, being placed through the hole in the transparency and an attachment point in the frame. Hundreds of fasteners may be used to attach the transparency to the frame. Typically, a fastener may be found around every inch along the transparency.
In manufacturing canopies, and in maintenance, it is desirable to determine whether cracks have occurred and/or propagated from any of the holes in the transparent material. Inspections of these holes may be made visually, in some cases. In many cases, an unaided viewer may be unable to see the hole clearly enough to determine whether cracks have occurred or propagated. The hole, however, in many cases, is obscured by the frame or other components in the canopy.
In some cases, a simple prism with a faceted surface may be used to reflect light rays to allow the viewer to see under or into the canopy frame to determine whether cracks have occurred or propagated from any of the holes where the transparent material is attached to the frame. This type of inspection system works in many cases. In some cases, however, the transparent material is located or positioned in the frame deep enough such that it is impractical or difficult to see whether cracks may have occurred or propagated. One manner in which the holes in the transparent material may be inspected, in this situation, is to disassemble portions of the canopy to expose the holes where the fastener attaching the transparent material to the frame of the canopy is located. The transparency, in some canopies, are bonded into the frame. With other canopies, the transparency may be attached with both fasteners and bonding. As a result, disassembly may be unfeasible with these types of designs.
Therefore, it would be advantageous to have a method and apparatus that overcomes these problems.